This invention relates generally to gas (particularly, air) valves, and more specifically, to magnetically-operated gas valves.
Ideally, a magnetically-operated valve should be compact, reliable, fast operating and capable of inexpensive manufacture. Prior art magnetic valves commonly use a movable needle having a resilient conical end cooperating with a conical valve seat such that insertion of the needle into the valve seat causes fluid-tight engagement of the conical surfaces thereof. It will be appreciated that needle-type valves require precise alignment between the needle and the opening therefor which contributes to relatively high manufacturing costs, and furthermore, adversely affects the reliability and longevity of the valves in use.
Any misalignment occurring by virtue of inherent manufacturing tolerances must be compensated for by using relatively strong springs to forcibly urge the needle into a fully seated condition, and additionally, misalignment may cause binding between the needle and valve seat, each of these conditions thereby placing commensurate demands upon the electromagnet if it is to unseat the needle in opposition to the relatively heavy springs and binding effects. Additionally, since a portion of the conical needle end extends into the opening, even after unseating of the needle, a relatively high lift or separation of the needle from the opening is required to permit restriction-free flow therethrough. This requirement for a high needle lift or excursion imposes an additional demand upon the electromagnet.
From a cost standpoint, it is highly desirable to minimize the demand made on the electromagnet so as to minimize the number of ampere-turns required. More particularly, the conductors utilized are generally of a highly conductive material, such as copper or aluminum, which are quite expensive. Therefore, it is desirable, from a cost standpoint, to limit the use thereof. It can be seen then that the high lift requirement and the binding propensity of needle-type valves contribute significantly to the costs of a magnetic valve by requiring a relatively high number of ampere-turns.
The disclosure of U.S. Pat. No. 3,726,315, issued to the inventor named herein, is hereby incorporated by reference herein. Said patent discloses an improved magnetic valve which is simple in construction, reliable, and most importantly, required fewer ampere-turns in its electromagnet than previous magnetic valves. More specifically, an exemplary magnetic valve according to said disclosure is provided with a movable valve element having a portion of magnetic material and including a flat surface portion cooperating with a valve seat. The implementation of a flat surfaced movable valve element allows unrestricted flow through the valve with smaller amounts of valve member lift or excursion than that required with competitive prior art devices. For example, the movable valve element may comprise a resilient member having a substantially flat surface portion for engaging the valve seat, and an armature member constructed of magnetic material on which the resilient member is mounted. The resilient member is mounted on the armature member in a manner to provide a predetermined relative movement therebetween so that the armature member may develop an initial velocity upon actuation of the valve prior to its acting upon the resilient member so that its inertia will overcome the seating force established by the pressure differential across the valve.
A synergistic effect is achieved in a valve according to said disclosure since the electromagnet will act unevenly on the armature member due to purposeful or inherent tolerance variations in the valve causing an uneven lifting of the armature which pries or peels the resilient member from the valve seat. Due to the combined result of the low excursion requirement, the inertia effect of the armature member, and the "prying" or "peeling" effect, a significantly lower magnetic flux density is required, and accordingly, the number of ampere-turns within the electromagnet are fewer than those of the competitive prior art devices of like purpose. As a consequence, a significant cost savings is achieved. As a still additional advantage, the alignment between the movable valve element and the valve seat is not critical, and accordingly assembly is economically and easily accomplished, tolerances are not critical, and dimensional variations due to wear have a minimal effect on the reliability and longevity of the device.
In accordance with one embodiment of the present invention, the armature member of such a magnetic air valve is provided with a non-magnetic covering or coating, preferably of a predetermined thickness. The non-magnetic covering serves as a non-magnetic gap, or an "artificial air gap", between the armature member and the electromagnet to control the magnetic flux force therebetween when the electromagnet is energized. The covering or coating or such embodiment preferably includes an inner layer of relatively inexpensive, easy-to-apply non-magnetic material and an outer layer of a relatively hard, wear resistant non-magnetic material. The inner layer is preferably composed of copper or a copper-containing substance, and the outer layer is preferably composed of electroless nickel.
The non-magnetic armature covering in the above-described embodiment is preferably formed by a method involving covering or plating the armature member with the first layer of non-magnetic material and tumbling the armature member to polish the same. Similarly, the armature member is then covered or plated with the outer layer of non-magnetic material and may also be tumbled in order to polish the same, if deemed necessary. Such final polishing is performed before the outer layer is heated for hardening.
In accordance with another embodiment of the invention, a non-magnetic wear plate is disposed between at least a portion of the electromagnet and the armature member to control the magnetic flux force therebetween when the electro-magnet is energized. The wear plate also substantially prevents the armature member from directly contacting, and thus wearing, such portion of the electromagnet when the electromagnet is energized. In this embodiment, the armature is preferably provided with only the above-mentioned outer layer of the relatively hard, wear resistant non-magnetic material.